Scientific investigation & inquiry skills

Year 7 answers

Fluency

Investigable question: one answerable by measurement. Hypothesis: a testable prediction linking cause to effect. IV: what the experimenter changes. DV: what is measured. CV: anything else kept the same.
Example: “If the ramp is raised higher, the car will roll a greater distance after leaving the ramp, because the car starts with more gravitational potential energy converted to kinetic energy.”
IV: ramp height. DV: distance rolled. CVs: same car, same surface, same starting point on ramp, same release (no pushing), same ramp material.
To reduce random error and identify anomalies by taking the mean of several readings.
(a) Line graph. (b) Bar graph. (c) Scatter plot.
A data point that does not fit the overall pattern of the results.
A list of possible hazards and how to control them, done before the experiment to keep the experimenter, others, and the environment safe.
Random: parallax when reading a meniscus. Systematic: a measuring cylinder miscalibrated so it reads $1$ mL too high.
A group treated exactly like the experimental groups except for the IV. It shows what happens without the “treatment” for comparison.
Larger samples average out random variation, making results more reliable and any real effect easier to detect.

Reasoning

An observation is what you directly see or measure (the leaf is yellow). An inference is an explanation you infer from the observation (the plant lacks nitrogen).
If several variables change at once, you cannot tell which caused the effect. Controlling variables isolates the IV as the only possible cause.
Writing it first prevents you from unconsciously shaping the design or interpretation to match the data — this is called confirmation bias.
Selecting “best” data misrepresents the experiment. Science requires honest reporting of all data, including outliers and disagreements with the hypothesis.
With more data, random variation cancels out more completely and any real pattern stands out more clearly from chance fluctuations.
Correlation without causation — both rise in summer because hot weather drives both independently. One does not cause the other.

Reasoning

IV: bottle colour (e.g. black, white, blue, red). DV: water temperature after $1$ hour. CVs: same bottle material and volume, same starting water temperature, same position in sun, same weather conditions, same thermometer, same time of day. Replicates: at least $3$ per colour.
Anomaly: $28$ . Possible causes: typo for $13$ or $14$ ; wrong shoot measured (a different species); a genetic variant in that plant; measurement taken at a different date.
Temperature vs time (time on x-axis, temperature on y-axis). Roughly flat at $0$ °C while the ice melts, then rising as the water warms. A line graph with a flat region then a rise.
IV: paper-towel brand. DV: mass of water absorbed (g). CVs: same piece size, same water volume, same dipping time, same squeezing. Replicates: $3$ strips per brand.

Reasoning

No. Alternative explanations: (i) students who eat breakfast may also sleep more or live in wealthier homes, and those factors drive both behaviours. (ii) students feeling good study more regularly and eat breakfast more regularly. A controlled experiment (randomly assigning students to eat or skip breakfast, with other conditions matched) would isolate the cause.
$102$ looks anomalous — pure water boils at $100$ °C at normal pressure. Mean with it: $(99+101+100+100+102)/5 = 100.4$ . Mean without: $(99+101+100+100)/4 = 100.0$ . The $100.0$ value is a better estimate if we suspect $102$ was a misreading or a calibration fault.
Without a control, you cannot tell if changes in the plants are due to the fertiliser or to other changes over time (weather, age, light). Some growth would happen anyway. A control group receiving no fertiliser lets you separate the fertiliser’s effect from natural growth.
IV: length of pendulum. DV: time for $10$ complete swings (divide by $10$ for period). CVs: same mass, same release angle, same location, same stopwatch. Procedure: tie string of known length, release from small angle, time $10$ swings, repeat $3$ times, calculate mean period. Vary length (e.g. $20, 40, 60, 80, 100$ cm). Graph: period increases with length, as a curve (square-root relationship).